This invention relates to power transmissions and, more particularly, to multi-speed power transmissions having three planetary gearsets and six torque-transmitting mechanisms for providing at least seven forward speed ratios.
Automatic shifting power transmissions are currently used in a majority of the vehicles produced in the United States. These vehicles generally employ three- and four-speed power transmissions. More recently, a trend towards more ratios, such as five- and six-speed power transmissions, has been proposed. In fact, some manufacturers do provide five-speed transmissions. Many of the vehicles utilizing manual type transmissions or countershaft type transmissions employ five- and six-speed power transmissions.
The five- and six-speed power transmissions provide improved vehicle acceleration performance and fuel economy when compared with three- and four-speed transmissions. There are many current patents that describe five- and six-speed power transmissions. Some of the six-speed power transmission patents, especially those assigned to the assignee of the present invention, describe six-speed power transmissions in families, wherein one or more family members incorporate a seven-speed power transmission. However, seven-speed power transmissions have not been proposed due to the complexity of these assemblies, as well as size and cost.
It is an object of the present invention to provide an improved family of power transmissions having three planetary gearsets and six torque-transmitting mechanisms.
In one aspect of the present invention, each of the planetary gearsets has three members including a sun gear member, a ring gear member, and a planet carrier assembly member.
In another aspect of the present invention, a first member of the first planetary gearset is continuously interconnected with a first member of the second planetary gearset and a first member of the third planetary gearset.
In yet another aspect of the present invention, a second interconnecting member continuously interconnects a second member of the first planetary gearset with a second member of the second planetary gearset.
In still another aspect of the present invention, a second member of the third planetary gearset is continuously interconnected with a stationary housing member.
In yet still another aspect of the present invention, a transmission output shaft is continuously connected with at least one member of one of the planetary gearsets.
In yet another aspect of the present invention, the transmission input shaft is not continuously connected with any member of the planetary gearsets.
In yet another aspect of the present invention, a first of the torque-transmitting mechanisms selectively interconnects the input shaft of the transmission with at least one member of one of the planetary gearsets.
In a further aspect of the present invention, a second of the torque-transmitting mechanisms selectively interconnects the transmission input shaft with at least one member of one of the planetary gearsets or with one of the interconnecting members.
In a yet further aspect of the present invention, a third of the torque-transmitting mechanisms selectively interconnects the input shaft of the transmission with at least one member of one of the planetary gearsets or one of the interconnecting members not otherwise interconnected with the second torque-transmitting mechanism.
In a still further aspect of the present invention, a fourth of the torque-transmitting mechanisms selectively interconnects at least one member of one of the planetary gearsets with either the input shaft, the output shaft, or another member of one of the planetary gearsets.
In a yet still further aspect of the present invention, a fifth of the torque-transmitting mechanisms selectively interconnects at least one member of one of the planetary gearsets with either another member of one of the planetary gearsets or with the transmission housing.
In another aspect of the present invention a sixth of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with either the output shaft, another member of one of the planetary gearsets, or with the transmission housing.
In still another aspect of the present invention, the six torque-transmitting mechanisms are selectively engageable in combinations of two to establish at least seven forward speed ratios and one reverse speed ratio between the input shaft and the output shaft of the transmission.